Diagnostic Pearls « QA Categories « Lake Washington Vascular

Should all AAA’s be fixed with stent-grafts?
Stent grafts are considered standard of care for many AAA patients, however it is not the only treatment, nor is it always the optimal for your patient. Factors that might influence whether the patient can have a stent graft include:

Anatomy of the aneurysm – the location must be sufficiently below the renal artery origins in order to allow proper sealing of the stent graft to normal (non-aneurysmal) aortic wall. Also, aortic “necks” (i.e. the portion above the aneurysm) must be relative straight (non-angulated) and free of thrombus and calcific plaque.

Anatomy of the iliac arteries – some iliac and femoral arteries are too small for patients to have the catheters passed from the groins. Although a larger incision to expose the iliac arteries directly can facilitate passing these catheters into the aorta, not all patients can have this done.

Longevity of the grafts – While the long-term data for endografts has shown excellent results (with equivalent mortality and freedom from aneurysm rupture compared to open surgery), we do know that they are subject to factors not typically seen with open surgical repairs. Endografts can migrate over time causing potential “leaks” of arterial blood back into the aneurysm sac. Small arteries (such as lumbar arteries or the inferior mesenteric artery), which are covered by the endograft, can continue to fill the aneurysm sac (called an endoleak). Graft components can eventually fail or lose their seal such that a leak of arterial blood flows back into the aneurysm. Any of these conditions, and possibly more, requires continuing follow up with imaging, essentially for the patient’s lifetime. Fortunately, abdominal duplex ultrasound offers a safe follow-up method, with CT angio reserved for some decision making if there is a potential problem identified. Future revisions (albeit minimally invasive, usually) are a definite possibility while a patient has an endograft in place. Because of these factors, some patients, especially those of relatively young age, may elect to have the open repair to avoid these possible complications.

I have an elderly gentleman with a large AAA (Abdominal Aortic Aneurysm). How old is too old for repair?

The advent of endovascular stent-graft repair as the mainstay of AAA repair has changed this line of thinking. Prior to endovascular stent-graft repair, most patients older than 75 were not recommended for surgery. With procedures done through small minimally invasive incision in the groins (avoiding an large abdominal incision), recovery is remarkably faster. Patients often are ambulating and eating normal diets within one post-op day. “Downtime” is significantly reduced, with full return to normal activity within days. Most importantly, perioperative morbidity and mortality of endovascular repaired are considerably reduced compared to open repair.

Given this new technology, our evaluation of patients for surgery is much more based on functional status (instead of absolute age cut-offs). Much of previous age limits for open repair were based on the idea of preventing a likely rupture over the next five to ten years. With open surgery, the risk of surgery was significant, especially in patients with advanced age; the perioperative morbidity recovery times especially with advanced age was prohibitive. This risk generally outweighed the relatively lower risk of mortality from a rupture over those 5-10 years.

With new endovascular repair, the overriding principle is still the prevention of a rupture. However, now without the quality of life “penalty” of a major surgery (i.e. with significantly reduced perioperative morbidity and with much faster recovery times to full functionality), the emphasis can now focus on prevention of rupture in the immediate sense (with decreased focus on patient’s long term life expectancy). Patients can now have freedom from rupture with less overall concern of age. A patient’s functional status (patient’s activity level and comorbidities) plays a very important role, as do overall surgical considerations.

My patient has an AAA (Abdominal Aortic Aneurysm). Shouldn’t it be fixed right away?

While a ruptured AAA is potentially catastrophic with extremely high mortality and morbidity, the natural history of AAA is fairly well understood. As a result we know the optimal timing for watching vs. repairing AAA. Timing of surgery is based on the maximum diameter of the aneurysm. Based on several large randomized control trials (RCTs), surgery for AAA did not confer a benefit for patients with 4.5 cm (neither survival benefit nor reduced risk from rupture). Those studies did show a definite statistical benefit from surgical repair of AAA greater than 5.5 cm.

We counsel our patients that timing of AAA surgery is based on optimal risk. While we can’t guarantee that a patient will not have a rupture when their aneurysm is less than 5 cm, we can say that the risk of a rupture at that size is statistically low enough that it does not outweigh the risk of surgery. Conversely, if one thinks of elective AAA repair as an operation to prevent a possible rupture, then there must be a high enough possibility of such a rupture to justify the surgery. The RCT’s mentioned above confirmed that the diameter at which the possibility of rupture was high enough to justify surgery and thus confer a survival benefit was 5.5 cm.

Most surgeons now agree that 5 cm AAA in a relatively young active patient will likely reach the 5.5 cm threshold and therefore is a candidate for repair. Conversely a large aneurysm in an elderly patient with poor functional status may not be a candidate for repair because of the patient’s overall survivability: whether he or she is more likely to die from comorbidities or the chance of a ruptured AAA.

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